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make object_directory.loose_objects_subdir_seen a bitmap

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There's no point in using 8 bits per-directory when 1 bit
will do.  This saves us 224 bytes per object directory, which
ends up being 22MB when dealing with 100K alternates.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Eric Wong 2021-07-07 23:10:17 +00:00 committed by Junio C Hamano
parent 407532f82d
commit 33f379eee6
2 changed files with 9 additions and 4 deletions
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11
object-file.c
View file

@ -2461,12 +2461,17 @@ struct oid_array *odb_loose_cache(struct object_directory *odb,
{
int subdir_nr = oid->hash[0];
struct strbuf buf = STRBUF_INIT;
size_t word_bits = bitsizeof(odb->loose_objects_subdir_seen[0]);
size_t word_index = subdir_nr / word_bits;
size_t mask = 1 << (subdir_nr % word_bits);
uint32_t *bitmap;
if (subdir_nr < 0 ||
subdir_nr >= ARRAY_SIZE(odb->loose_objects_subdir_seen))
subdir_nr >= bitsizeof(odb->loose_objects_subdir_seen))
BUG("subdir_nr out of range");
if (odb->loose_objects_subdir_seen[subdir_nr])
bitmap = &odb->loose_objects_subdir_seen[word_index];
if (*bitmap & mask)
return &odb->loose_objects_cache[subdir_nr];
strbuf_addstr(&buf, odb->path);
@ -2474,7 +2479,7 @@ struct oid_array *odb_loose_cache(struct object_directory *odb,
append_loose_object,
NULL, NULL,
&odb->loose_objects_cache[subdir_nr]);
odb->loose_objects_subdir_seen[subdir_nr] = 1;
*bitmap |= mask;
strbuf_release(&buf);
return &odb->loose_objects_cache[subdir_nr];
}

2
object-store.h
View file

@ -22,7 +22,7 @@ struct object_directory {
*
* Be sure to call odb_load_loose_cache() before using.
*/
char loose_objects_subdir_seen[256];
uint32_t loose_objects_subdir_seen[8]; /* 256 bits */
struct oid_array loose_objects_cache[256];
/*